The present invention relates broadly to a flexible, ultra high pressure reinforced thermoplastic hose construction, and more particularly to such a hose construction which is provided to be especially kink resistant by virtue of having an innermost reinforcement layer which is spiral wound over a tubular core as a composite of metal wire and non-metallic, synthetic fiber elements.
Flexible high-pressure hose is used in a variety of fluid transfer applications such as in the water blast removal of paint or concrete, and in sewer cleaning operations. As used herein, "high-pressure" is ascribed herein its common trade definition of hydraulic pressures greater than about 10 MPa, with "ultra" high being used herein to designate pressures greater of about 100 MPa or more.
In basic structure, hoses of the type herein involved typically are constructed as having a tubular core surrounded by one or more reinforcement layers or courses of high tensile strength steel wire and/or synthetic fiber. The reinforcement layers, in turn, are protected by a surrounding outer sheath or cover which may be of the same or different material as the core tube. The cover also provides the hose with increased abrasion resistance.
The core tube, which may be a thermoplastic material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane, or a synthetic rubber material such as Buna N or neoprene, is conventionally extruded and cooled or cured. As is detailed in U.S. Pat. Nos. 3,116,760; 3,159,183; 3,966,238; 4,952,262, if necessary, the tube may be cross-head extruded over a mandrel for support, or otherwise supported in later forming operations using air pressure and/or reduced processing temperatures.
From the extruder, the tube may be collected on a reel or other take-up device for further processing. As dispensed from the reel, the tube optionally next may be passed through an applicator for its coating with an outer layer of an adhesive material which, in the case of thermoplastic hose, may be a polyurethane or other isocyanate-based adhesive, or, in the case of "rubber," i.e., vulcanizable elastomeric, hose, an vulcanizable adhesion promoter. The core tube then may be delivered through a braider and/or a spiral winder for its reinforcement with one or more surrounding layers of wire and/or fibrous material such as a monofilament, yarn, or roving. These reinforcement layers, which are applied under tension and which may be bonded to the core and to adjacent reinforcement layers, typically comprise an interwoven braid or a spiral winding of a nylon, polyester, or aramid yarn, or a high tensile steel or other metal wire.
Following the application of the reinforcement layers, the outer cover or sheath optionally may be applied. Such cover, which may be formed as a cross-head extrusion or a spiral-wound wrapping, typically comprises an abrasion-resistant polymeric material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane. As before, an adhesive layer may be used to bond the outer cover to the reinforcement layers.
Representative high-pressure spiral wound and other hose constructions, as well as manufacturing methods therefor, are shown in U.S. Pat. Nos. 4,384,595; 4,537,222; 4,317,000; 3,791,415; 4,175,992; 4,241,763; 4,585,035; 5,024,252; 4,952,262; 4,444,707; 3,805,848; 3,790,419; 3,566,924; 5,361,806; 3,654,967; 4,259,991; 4,850,395; 3,905,398; 5,062,456; 4,898,212; 4,699,178; and 4,343,333. Heretofore, however, it is believed that an ultra high pressure hose, that is, having a working pressure of about 100 MPa or more which was both flexible and highly kink resistant was unknown in the art. That is, although high pressure hoses could be made kink-resistant by increasing the wall thickness thereof with thicker core tubes and additional reinforcement layers, such hoses could not be considered "flexible" in failing to meet commercial bend radius requirements. By "kinking," it is meant that the wall of the hose is pinched or otherwise collapses to close or otherwise restrict the inner diameter of the hose.
Further with respect to high pressure thermoplastic hose constructions, it is known that the high strength thermoplastic materials used in such constructions are, necessarily, rigid. In service, high pressure thermoplastic hoses, and particularly such hoses utilizing multiple steel wire reinforcement layers and higher performance thermoplastics such as polyamides, therefore may exhibit relatively poor flexural properties as compared to rubber hose.
In view of the foregoing, it will be appreciated that ultra high pressure hose constructions must exhibit a demanding balance of mechanical and other physical properties for proper performance. Indeed, as commercial applications for ultra high pressure hoses have increased as a less labor intensive and, therefore, more economical substitute for rigid metal pipe, there have been calls from industry for further improvements in such hoses and in the materials of construction therefor. Especially desired would be a construction which is flexible, yet resistant to kinking in critical applications such as waster blasting and sewer cleaning.